The term "absorbent article" relates to products such as sanitary napkins, incontinent products, diapers, panty liners, training pants and the like. Sanitary napkins, also referred to as catamenial or feminine pads, are designed to be worn by a female to absorb medium to heavy flow of body fluids such as menses, blood, urine, and other excrements discharged by the body during a menstrual period. Sanitary napkins are external devices which are designed to be aligned approximate to the pudendum region of the human body and are generally held in position by being adhesively or mechanically attached to an undergarment. Such products differ from tampons which are classified as internal devices and are designed to be physically inserted into the vaginal cavity. Sanitary napkins also differ from pantiliners and panty shields in several noticeable ways. Most sanitary napkins are generally larger in size, have a more defined three-dimensional configuration, are thicker in caliper and are bulkier in appearance than pantiliners or panty shields. Functionally, sanitary napkins are different in that they are constructed to absorb a greater quantity of body fluid and are designed so that they can be worn for a longer period of time, for example, overnight if needed.
Since sanitary napkins are normally used during the major discharge portion of a menstrual period, they are constructed to handle medium to heavy flows and commonly have a total absorbent capacity in the range of about 20 to 50 grams of fluid. Pantiliners and panty shields, on the other hand, are designed to absorb relatively small amounts of body fluids and are marketed to be used at the beginning and end of a menstrual period when flow is light or spotty. Commercially available pantiliners and panty shields are constructed to have a total absorbent capacity in the range of about 1 to 15 grams of fluid.
Today's sociological changes have led to more women becoming active in sports and other types of physical activity. These changes have been accompanied by a change in attire and have led to more women wearing tight, body-fitting clothing. Most current sanitary napkins, having a caliper of 6.4 mm. or greater, can present an unsightly bulge adjacent the pudendum when worn inside tight-fitting shorts or pants. The overall size and configuration of the napkin can also restrict leg movement or cause discomfort when a woman participates in physical or sporting events. In view of this, there is a real need to provide an improved thin sanitary napkin which is less than about 5 millimeters in caliper and resists bunching and twisting when worn.
In providing a thin sanitary napkin less than about 5 millimeters in caliper, it was found that such products had a tendency to bunch and twist when worn. The squeezing of the napkin between the thighs and the resulting deformation as a woman moves about, causes the upper surface of the napkin to acquire a curved or convex shape. The twisting is sometimes referred to as "roping" because of twisting along a longitudinal axis that imparts a cylindrical profile to the sanitary napkin. The roping effect is detrimental because the napkin is unable to absorb body fluid that contacts its upper surface. The fluid discharged from the vagina has a tendency to run off the roped napkin before it can be absorbed by the primary absorbent means in the sanitary napkin and, therefore, the fluid leaks on an adjacent undergarment. This run-off becomes significant during periods of heavy flow. Such bunching and twisting is more of a problem in thin sanitary napkins than in thicker napkins.
Other people have recognized the need for a thin sanitary napkin. See, for example: U.S. Pat. Nos. 4,217,901 to Bradstreet et al.; 4,950,264 and 5,009,653 to Osborn; and U.S. Pat. No. 5,248,309 to Serbiak et al. assigned to the same owner as this Patent Application.